DESCRIPTION (adapted from the Abstract): In this AIDS-FIRCA application the Principal Investigator proposes a collaboration between the Western New Englan Pediatric AIDS Clinical Trials Unit (WNEPACTG) at the University of Massachusetts Medical center, Worcester, Massachusetts and the Department of pediatrics and Child Health at the University of Natal, Durban, South Africa. This collaboration will examine the relationship between maternal co-infection with HIV and tuberculosis and the vertical transmission of HIV-1. These center have informally collaborated since 1992 and members of the research team have exchanged reciprocal visits to each other's institutions over the past five years. Currently, the prevalence of HIV infection among women receiving prenatal care at King Edward VIII Hospital in Durban is 25-30 percent. In 1996 12,000 deliveries were performed and 11 neonates were identified with bacteriological confirmed tuberculosis (TB) were identified. The proposed study will focus on the pathogenesis of HIV infection. The specific aims of this AIDS-FIRCA collaboration are: (1) to establish the vertical transmission rate and timing of HIV-1 transmission in the presence of maternal HIV-1 alone and in the presence of maternal co-infection with HIV and TB; (2) to determine whether neonatal HIV-1 disease progression is more rapid, and death earlier, in neonates born of mothers with TB and HIV-1 co-infection as opposed to those born of mothers with HIV-1 infection alone; (3) to determine whether maternal HIV-1 viral load in plasma as well as in vaginal secretions influences the vertical transmission of TB and HIV-1.